Hollow body organs are shaped in particular native ways to perform specific native functions. When a body organ looses its native shape due to disease, injury, or simply the natural aging process, the native functions can be adversely affected. The heart serves as a good example of this marriage between native shape and native function, as well as the dysfunctions that can occur should the native shape change.
I. The Anatomy of a Healthy Heart
The heart (see FIG. 1) is slightly larger than a clenched fist. It is a double (left and right side), self-adjusting muscular pump, the parts of which work in unison to propel blood to all parts of the body. The right side of the heart receives poorly oxygenated (“venous”) blood from the body from the superior vena cava and inferior vena cava and pumps it through the pulmonary artery to the lungs for oxygenation. The left side receives well-oxygenation (“arterial”) blood from the lungs through the pulmonary veins and pumps it into the aorta for distribution to the body.
The heart has four chambers, two on each side—the right and left atria, and the right and left ventricles. The atria are the blood-receiving chambers, which pump blood into the ventricles. A wall composed of membranous and muscular parts, called the interatrial septum, separates the right and left atria. The ventricles are the blood-discharging chambers. A wall composed of membranous and muscular parts, called the interventricular septum, separates the right and left ventricles.
The synchronous pumping actions of the left and right sides of the heart constitute the cardiac cycle. The cycle begins with a period of ventricular relaxation, called ventricular diastole. The cycle ends with a period of ventricular contraction, called ventricular systole.
The heart has four valves (see FIGS. 2 and 3) that ensure that blood does not flow in the wrong direction during the cardiac cycle; that is, to ensure that the blood does not back flow from the ventricles into the corresponding atria, or back flow from the arteries into the corresponding ventricles. The valve between the left atrium and the left ventricle is the mitral valve. The valve between the right atrium and the right ventricle is the tricuspid valve. The pulmonary valve is at the opening of the pulmonary artery. The aortic valve is at the opening of the aorta.
At the beginning of ventricular diastole (i.e., ventricular filling) (see FIG. 2), the aortic and pulmonary valves are closed to prevent back flow from the arteries into the ventricles. Shortly thereafter, the tricuspid and mitral valves open (as FIG. 2 shows), to allow flow from the atria into the corresponding ventricles. Shortly after ventricular systole (i.e., ventricular emptying) begins, the tricuspid and mitral valves close (see FIG. 3)—to prevent back flow from the ventricles into the corresponding atria—and the aortic and pulmonary valves open—to permit discharge of blood into the arteries from the corresponding ventricles.
The heart valves are defined by fibrous rings of collagen, each called an annulus, which forms a part of the fibrous skeleton of the heart. The annulus provides attachments for the cusps or leaflets of the valves. In a healthy heart, muscles and their tendinous chords (chordae tendineae) support the valves, allowing the leaflets of the valves to open and close in accordance with their intended functions.
II. Heart Dysfunctions
Infection, myocardial infarction, atrial fibrillation, other diseases, or anatomic defects can adversely affect the normal synchronous pumping actions of the left and right sides of the heart and/or the operation of heart valves during the cardiac cycle.
For example, due to one or more of these causes, a heart chamber may become stretched and enlarged. This condition can lead to adverse consequences. For example, (1) due to its enlarged condition the heart must pump harder to move the blood, and/or too little blood may move from the heart to the rest of the body. Over time, other chambers of the heart may also become weaker. The stretching and enlargement of a heart chamber, e.g., in the left ventricle, can lead to a condition called congestive heart failure. If not treated, congestive heart failure can lead to pulmonary embolisms, circulatory shutdown, and death.
The enlargement of a heart chamber can also lead to the enlargement or stretching a heart valve annulus. Also, the stretching or tearing of the chords surrounding a heart valve, or other forms of muscle failure in this region, can also change the shape of a heart valve annulus, even when enlargement of a heart chamber is absent. When the heart valve annulus changes its shape, the valve leaflets can fail to coapt. An undesired back flow of blood can occur between an atrium and a ventricle (called regurgitation), or back flow between an artery and a ventricle can occur. Such dysfunctions can eventually also weaken the heart and can result in heart failure.
Anatomic defects, e.g., in the septum, can also lead to heart dysfunction. These defects can be congenital, or they can result from disease or injury.
III. Prior Treatment Modalities
Medications can be successful in treating heart dysfunctions. For chronic or acute dysfunction, however, surgery is often necessary. For congestive heart failure, a heart transplant may be required. Like invasive, open heart surgical approaches have been used to repair or replace a dysfunctional heart valves or to correct septal defects.
The need remains for simple, cost-effective, and less invasive devices, systems, and methods for treating heart conditions such as congestive heart failure and/or heart valve dysfunction and/or septal defects. A parallel need also remains for similarly treating other dysfunctions that arise from unintended shape changes in other body organs.